Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF REDUCING MAPPING OF AN
ELECTRODEPOSITABLE COATING LAYER
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Application No.
61/187,298
filed June 16, 2009, which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of reducing mapping of a
coating layer
deposited onto a substrate.
BACKGROUND INFORMATION
[0003] In the Automotive and Industrial OEM industries, a substrate is
typically
pretreated with a pretreatment coating composition and rinsed with a rinsing
solution, such as
deionized water, prior to application of an electrodepositable coating
composition onto the
substrate. While the pretreatment coating composition is applied onto the
substrate to increase
the adhesion of subsequently deposited coatings, one of the potential
drawbacks of using certain
types of pretreatment coating compositions is that it can lead to "mapping" in
the
electrodepositable coating layer that is deposited from an electrodepositable
coating composition.
"Mapping" is the phenomenon that occurs when topcoats are subsequently applied
to such
electrodepositable coating layer and the differences in film thickness of the
electrodeposition
coating layer can telegraph through the topcoats, thereby creating an
undesirable topcoat
appearance.
SUMMARY OF THE INVENTION
[0004] The present invention is directed to a method of coating a substrate
comprising:
depositing a first coating composition onto at least a portion of the
substrate, said first coating
composition comprising: (i) a group IIIB metal, a group IVB metal, or
combinations thereof;
depositing a second coating composition onto at least a portion of the first
coating composition,
said second coating composition comprising: (a) an active hydrogen containing
ionic salt group
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containing resin comprising reactive functional groups; (b) a crosslinking
agent reactive with at
least one of the reactive functional groups of the resin; and (c) a soluble
alkaline earth metal
present in an amount of not more than 1000 parts per million, based on the
total weight of the
second coating composition.
[0005] The present invention is also directed to a coating system comprising:
a first
coating layer deposited onto at least a portion of a substrate wherein said
first coating layer is
deposited from a first coating composition comprising: (i) a group IIIB metal,
a group IVB metal,
or combinations thereof; and a second coating layer deposited onto at least a
portion of the first
coating layer wherein said second coating layer is deposited from a second
coating composition
comprising: (a) an active hydrogen containing ionic salt group containing
resin comprising
reactive functional groups; (b) a crosslinking agent reactive with at least
one of the reactive
functional groups of the resin; and (c) a soluble alkaline earth metal present
in an amount of not
more than 1000 parts per million, based on the total weight of the second
coating composition.
DETAILED DESCRIPTION
[0006] As used herein, unless otherwise expressly specified, all numbers such
as those
expressing values, ranges, amounts or percentages may be read as if prefaced
by the word
"about", even if the term does not expressly appear. When referring to any
numerical range of
values, such ranges are understood to include each and every number and/or
fraction between the
stated range minimum and maximum. For example, a range of "1 to 10" is
intended to include all
sub-ranges between (and including) the recited minimum value of 1 and the
recited maximum
value of 10, that is, having a minimum value equal to or greater than 1 and a
maximum value of
equal to or less than 10. As employed herein, the term "number" means one or
an integer greater
than one.
[0007] As used herein, plural phrases or terms encompasses their singular
counterparts
and vice versa, unless specifically stated otherwise. By way of illustration,
and not limitation,
although reference is made herein to "a" soluble rare earth metal, a plurality
of these rare earth
metals may be used in the present invention. As used herein, "plurality" means
two or more.
[0008] As used herein, "includes" and like terms means "including without
limitation."
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[0009] As used herein, the use of "or" means "and/or" unless specifically
stated otherwise,
even though "and/or" may be explicitly used in certain instances.
[0010] As used herein, "molecular weight" means weight average molecular
weight (Mw)
as determined by Gel Permeation Chromatography.
[0011] As used herein, the term "cure" refers to a coating wherein any
crosslinkable
components of the composition are at least partially crosslinked. In certain
embodiments, the
crosslink density of the crosslinkable components (i.e., the degree of
crosslinking) ranges from
5% to 100%, such as 35% to 85%, or, in some cases, 50% to 85% of complete
crosslinking. One
skilled in the art will understand that the presence and degree of
crosslinking, i.e., the crosslink
density, can be determined by a variety of methods, such as dynamic mechanical
thermal analysis
(DMTA) using a Polymer Laboratories MK III DMTA analyzer conducted under
nitrogen.
[0012] Reference to any monomer(s) herein refers generally to a monomer that
can be
polymerized with another polymerizable component such as another monomer or
polymer.
Unless otherwise indicated, it should be appreciated that once the monomer
components react
with one another to form a compound, the compound will comprise the residues
of the monomer
components.
[0013] As used herein, a "substantially solvent free environment" means that
trace or
incidental amounts of organic solvent, such as < 5 weight % or < 3 weight % or
< 1 weight %
based on all of the ingredients used in the reaction mixture, can be present.
METHOD OF COATING A SUBSTRATE
[0014] The present invention is directed to a method of applying various
coating
compositions onto a surface of substrate. The various coating composition
disclosed herein, in
some instances, are selected to reduce and/or eliminate the "mapping" effect
described above.
[0015] In certain embodiments, the present invention is directed to a method
of coating a
substrate comprising: (1) depositing a first coating composition onto at least
a portion of the
substrate, said first coating composition comprising: (i) a group IIIB metal,
a group IVB metal, or
combinations thereof; and (2) depositing a second coating composition onto at
least a portion of
the first coating composition, said second coating composition comprising: (a)
an active hydrogen
containing ionic salt group containing resin comprising reactive functional
groups; (b) a
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crosslinking agent reactive with at least one of the reactive functional
groups of the resin; and (c)
a soluble alkaline earth metal ion present in an amount of not more than 1000
parts per million,
based on the total weight of the second coating composition.
[0016] The substrate to be coated in accordance with the methods of the
present invention
may first be cleaned to remove grease, dirt, or other extraneous matter using
techniques known in
the art. For example, mild or strong alkaline cleaners, which are commercially
available and
conventionally used in metal pretreatment processes, can be used to clean at
least a portion of the
surface of the substrate. Examples of alkaline cleaners suitable for use in
the present invention
include Chemkleen 166HP and Chemkleen 2010LP, both of which are commercially
available
from PPG Industries, Inc. Such cleaners are often followed and/or preceded by
a rinsing step in
which a rinsing solution, such as water (including deionized water), is
applied onto the substrate.
First Coating CoMposition:
[0017] As described above, the method of the present invention entails
depositing a first
coating composition onto at least a portion of the substrate. In certain
embodiments, the first
coating composition is a pretreatment coating composition. As used herein,
"pretreatment
coating composition" refers to a composition that chemically alters the
surface of a bare metal
substrate. The first coating composition comprises: (i) a group IIIB metal, a
group IVB metal, or
a combination thereof. As used herein, the terms "group IIIB metal" and "group
IVB metal" refer
to the elements that are in group IIIB and group IVB of the CAS Periodic Table
of Elements as
shown, for example in the Handbook of Chemistry and Physics, 63rd edition
(1983). As used
herein, the term "group IIIB metal compound" or "group IVB metal compound"
refers to
compounds that comprise at least one element that is in group IIIB or group
IVB of the CAS
Periodic Table of Elements. While, in certain embodiments, the source of the
IIIB and/or IVB
metal is the metal itself (e.g., zirconium, titanium, hafnium, yttrium,
cerium, or combinations
thereof), group IIIB and/or IVB compounds may also be used as the source of
the IIIB and/or
IVB metal. Suitable IIIB and/or IVB compounds include hexafluorozirconic acid,
alkali metal
and ammonium salts thereof, ammonium zirconium carbonate, zirconyl nitrate,
zirconium
carboxylates and zirconium hydroxy carboxylates, such as hydrofluorozirconic
acid, zirconium
acetate, zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium
lactate,
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ammonium zirconium citrate, fluorotitanic acid and its salts, hafnium nitrate,
yttrium nitrate,
cerous nitrate, or combinations thereof.
[0018] In certain embodiments, the group IIIB and/or group IVB metal compound
is
present in the first coating composition in an amount of 10 to 5000 parts per
million ("ppm")
metal, such as 100 to 300 ppm metal, based on the total weight of the first
coating composition.
The pH of the first coating composition often ranges from 2.0 to 7.0, such as
3.5 to 5.5. The pH
of the first coating composition may be adjusted using mineral acids, such as
hydrofluoric acid,
fluoroboric acid, phosphoric acid, and the like, including mixtures thereof;
organic acids, such as
lactic acid, acetic acid, citric acid, or mixtures thereof; and water soluble
or water dispersible
bases, such as sodium hydroxide, ammonium hydroxide, ammonia, or amines, such
as
triethylamine, methylethyl amine, diisopropanolamine, or a mixture thereof.
[0019] In certain embodiments, the first coating composition also comprises a
copper
compound. While, in some embodiments, the source of copper in the copper
compound is the
metal itself, both water soluble and insoluble copper compounds may be used as
the source of the
copper compound in the first coating composition. As used herein, "copper
compound" refers to
compounds that comprise copper. Suitable water soluble and/or water insoluble
copper
compounds include copper cyanide, copper potassium cyanide, copper sulfate,
copper nitrate,
copper pyrophosphate, copper thiocyanate, disodium copper
ethylenediaminetetraacetate
tetrahydrate, copper bromide, copper oxide, copper hydroxide, copper chloride,
copper fluoride,
copper gluconate, copper citrate, copper lauroyl sarcosinate, copper formate,
copper acetate,
copper propionate, copper butyrate, copper lactate, copper oxalate, copper
phytate, copper
tartarate, copper malate, copper succinate, copper malonate, copper maleate,
copper benzoate,
copper salicylate, copper aspartate, copper glutamate, copper fumarate, copper
glycerophosphate,
sodium copper chlorophyllin, copper fluorosilicate, copper fluoroborate and
copper iodate, as
well as copper salts of carboxylic acids in the homologous series formic acid
to decanoic acid,
copper salts of polybasic acids in the series oxalic acid to suberic acid, and
copper salts of
hydroxycarboxylic acids, including glycolic, lactic, tartaric, malic and
citric acids, or combinations
in any of the foregoing. In certain embodiments, the copper compound is added
as a complex salt
such as those described in U.S. Patent Publication No. 2009/0084682 in
paragraph [0020], the
cited portion of which being incorporated herein by reference.
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[0020] When copper ions supplied from such a water-soluble copper compound are
precipitated as an impurity in the form of copper sulfate, copper oxide, etc.,
it may be desirable to
add a complexing agent that suppresses the precipitation of copper ions, thus
stabilizing them as a
copper complex in the solution. Suitable complexing agents include those
described in U.S.
Patent Publication No. 2009/0084682 in paragraph [0021], the cited portion of
which being
incorporated herein by reference.
[0021] In certain embodiments, the copper compound is included in the first
coating
composition in an amount from 1 ppm to 5,000 ppm, such as 1 ppm to 500 ppm,
or, in some
cases, 1 ppm to 50 ppm of total copper (measured as elemental copper), based
on the total weight
of the ingredients in the first coating composition.
[0022] In some embodiments, the first coating composition can also comprise
the various
materials, such as the binder, and surfactants as described in paragraphs
[0025] to [0028] of U.S.
Patent Publication No. 2008/0145678, which is incorporated herein by
reference.
[0023] In certain embodiments, the first coating composition also comprises a
silane, such
as, for example, an amino group-containing silane coupling agent, a
hydrolysate thereof, or a
polymer thereof, as described in U.S. Patent Publication No. 2004/0163736 at
[0025] to [0031],
the cited portion of which being incorporated herein by reference. In other
embodiments of the
present invention, however, the first coating composition is substantially
free, or, in some cases,
completely free of any such amino group-containing silane coupling agent. As
used herein, the
term "substantially free", when used with reference to the absence of amino-
group containing
silane coupling agent in the first coating composition, means that any amino-
group containing
silane coupling agent, hydrolysate thereof, or polymer thereof that is present
in the pretreatment
composition is present in an amount of less than 5 ppm. As used herein, the
term "completely
free" means that there is no amino-group containing silane coupling agent,
hydrolysate thereof, or
polymer thereof in the first coating composition at all.
[0024] In certain embodiments, the first coating composition also comprises a
reaction
accelerator, such as nitrite ions, nitro-group containing compounds,
hydroxylamine sulfate,
persulfate ions, sulfite ions, hyposulfite ions, peroxides, iron (III) ions,
citric acid iron compounds,
bromate ions, perchlorinate ions, chlorate ions, chlorite ions as well as
ascorbic acid, citric acid,
tartaric acid, malonic acid, succinic acid and salts thereof, or combinations
thereof. Specific
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examples of suitable materials and their amounts are described in U.S. Patent
Publication No.
2004/0163736 in paragraphs [0032] to [0041], the cited portion of which being
incorporated
herein by reference.
[0025] In certain embodiments, the first coating composition also includes a
source of
phosphate ions. Suitable amounts of phosphate ions and suitable sources of
such ions are
described in U.S. Patent Publication No. 2009/0032144 in paragraph [0043], the
cited portion of
which being incorporated herein by reference. In other embodiments, however,
the first coating
composition is substantially or, in some cases, completely free of phosphate
ions. As used herein,
the term "substantially free" when used in reference to the absence of
phosphate ions in the first
coating composition, means that phosphate ion is present in the composition in
an amount of less
than 10 ppm based on the total weight of the first coating composition. As
used herein,
"completely free", when used with reference to the absence of phosphate ions,
means that there
are no phosphate ions in the first coating composition at all.
[0026] In certain embodiments, the first coating composition is substantially
or, in some
cases, completely free of chromate and/or heavy metal phosphate, such as zinc
phosphate. As
used herein, the term "substantially free" when used in reference to the
absence of chromate
and/or heavy metal phosphate in the pretreatment composition, means that these
substances are
present in an amount of less than 10 ppm based on the total weight of the
first coating
composition. As used herein, the term "completely free", when used with
reference to the absence
of a heavy metal phosphate and/or chromate, means that there is no heavy metal
phosphate and/or
chromate in the first coating composition at all.
[0027] Moreover, in certain embodiments, the first coating composition is
substantially
free, or, in some cases, completely free of any organic materials. As used
herein, the term
"substantially free", when used with reference to the absence of organic
materials in the
composition, means that any organic materials are present in the composition,
if at all, as an
incidental impurity. In other words, the presence of any organic material does
not affect the
properties of the composition. As used herein, the term "completely free",
when used with
reference to the absence of organic material, means that there is no organic
material in the
composition at all.
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[0028] In some embodiments, the first coating composition further comprises
(iii) free
fluorine and (iv) a metal fluoride salt formed from a metal and/or metal
compound which forms a
fluoride salt. The metal that forms the metal fluoride salt is supplied in an
amount sufficient to
maintain the level of free fluorine in the first coating composition at a
level ranging from 0.1 ppm
to 300 ppm based on the total weight of the first coating composition. As used
herein, "free
fluorine" means isolated fluorine ion and its concentration in the first
coating composition.
Suitable sources of fluorine include those described in U.S. Patent
Publication No. 2009/0032144
in paragraphs [0027] to [0028], the cited portion of which being incorporated
herein by reference.
In some embodiments, the metal fluoride salt that is formed has a pKsp of at
least 11, such as at
least 15 or at least 20. As used herein, "plop" refers to the inerse log of
the solubility product
constant for a compound. In the present invention, a metal and/or metal
containing compound is
selected such that it forms a fluoride salt having a plop of at least 11. For
purposes of this
invention, the pKsp value for a metal fluoride salt refers to the pKsp values
reported in Lange's
Handbook of Chemistry, 15th Ed., McGraw-Hill, 1999, Table 8.6. In certain
embodiments, the
metal and/or metal compound which forms a fluoride salt having a pKsp of at
least 11 is selected
from cerium (pKp of CeF3 is 15.1), lanthanum (pKp of LaF3 is 16.2), scandium
(pKp of ScF3 is
23.24), yttrium (pKp of Y3 is 20.06), or mixture thereof. In certain
embodiments, the metal
and/or metal compound can be present in the first coating composition in an
amount ranging from
0.1 ppm to 300 ppm, such as from 20 ppm to 100 ppm.
[0029] In some embodiments, the first coating composition can further comprise
a yttrium
containing compound such as those described in U.S. Patent Publication No.
2009/0032144 in
paragraph [0033], the cited portion of which being incorporated herein by
reference.
[0030] Additionally, in certain embodiments, the first coating composition can
comprise
one or more additional "electropositive metals" as described in U.S. Patent
Publication No.
2009/0084682 in paragraphs [0014] to [0015], the cited portion of which being
incorporated
herein by reference.
[0031] After application of the first coating composition on at least a
portion of the
substrate, the first coating composition can, optionally, be rinsed with
water, such as deionized
water. Alternatively, at least a portion of the first coating composition,
immediately or after a
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drying period at ambient or elevated temperature conditions, may be coated
with the second
coating composition described below.
Second Coating CoMposition:
[0032] As stated above, the present invention also includes the deposition of
a second
coating composition onto at least a portion of the first coating composition.
The second coating
composition comprises (a) an active hydrogen containing ionic salt group
containing resin
comprising reactive functional groups; (b) a crosslinking agent reactive with
at least one of the
reactive functional groups of the resin; and (c) a soluble alkaline earth
metal ion present in an
amount of not more than 1000 ppm, such as from 5 ppm to 750 ppm, 5 ppm to 500
ppm, or 5
ppm to 100 ppm, based on the total weight of the second coating composition.
As used herein,
"an alkaline earth metal ion" means a metal ion of a Group IIA metal, such as
Bat+, Sr2+, Mgt+,
Cat+, Be 2+ or Rae+. More preferably, "an alkaline earth metal ion" means a
metal ion of a Group
IIA metal such as Ba2+ or Sr 2+ or mixtures thereof. In certain embodiments,
the alkaline earth
metal ion results from the dissociation of a metal compound, such as a soluble
metal compound,
in an aqueous medium (e.g., electrodeposition bath). As used herein, "soluble
metal compound"
refers to a metal compound, typically an alkaline earth metal compound,
capable of substantially
complete dissociation in an aqueous medium. Examples of suitable soluble metal
compounds that
may be used in the present invention include those listed in U.S. Patent
Publication No.
2004/0050704 in paragraph [0018], the cited portion of which being
incorporated herein by
reference.
[0033] In some embodiments, the second composition can further comprise
"insoluble
metal compounds" such as those listed in U.S. Patent Publication No.
2004/0050704 in paragraph
[0018]. As used herein, "insoluble metal compound" refers to a metal compound,
typically a rare
earth metal compound, capable of only partial dissociation in an aqueous
medium.
[0034] In certain embodiments, the second coating composition can further
comprise
additional metal compounds, which may be advantageous in minimizing "mapping,"
such as those
described in U.S. Patent Publication No. 2004/0050704 in paragraph [0019], the
cited portion of
which being incorporated herein by reference.
[0035] In certain embodiments, the second coating composition can further
comprise a
corrosion inhibitor based on compounds containing metals such as yttrium,
bismuth, zinc, cerium,
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aluminum, silicon, calcium, rare earth elements, and magnesium. These
corrosion inhibitors may
be present in an amount between about 50 and 10,000 ppm total metal based on
the total weight
of the second coating composition.
[0036] In addition to those components described above, the second coating
composition
can further comprise the main film-forming polymer (e.g., active hydrogen
containing polymer),
curing agent (i.e., crosslinking agent), and bismuth compound(s), described in
U.S. Patent
Publication No. 2004/0050704 in paragraphs [0021] to [0033], the cited portion
of which being
incorporated herein by reference. As used herein, the phrase "reactive
functional group" of the
active hydrogen containing polymer means hydroxyl, carboxyl, carbamate, epoxy,
isocyanate,
aceto acetate, amine, mercaptan, or combinations thereof. Suitable
crosslinking agents, in addition
to the ones referred to above, also include polyepoxides, beta-
hydroxyalkylamides, polyacids,
anhydrides, organometallic acid-functional materials, polyamines, polyamides,
cyclic carbonates,
siloxanes, or combinations thereof.
[0037] In certain embodiments, the second coating composition is an
electrodeposition
coating composition that is contained forms at least a portion of an
electrodepositable bath. The
electrodepositable bath disclosed herein is typically supplied as two
components: (1) a main
vehicle ("clear resin feed") and (2) a grind vehicle ("pigment paste"). In
general, (1) the main
vehicle comprises (a) a film forming polymer ("an active hydrogen-containing
ionic salt group-
containing resin"), (b) a crosslinking agent, and (c) any additional water-
dispersible, non-
pigmented components (e.g., catalysts, hindered amine light stabilizers). In
general, (2) the grind
vehicle comprises (d) one or more pigments (e.g., titanium dioxide, carbon
black), (e) a water-
dispersible grind resin, which can be the same or different from the film
forming polymer, and,
optionally, (f) additives such as catalysts, antioxidants, biocides,
defoamers, surfactants, wetting
agents, dispersing aids, clays, hindered amine light stabilizers, UV light
absorbers and stabilizers,
or combinations thereof. The electrodeposition bath is typically prepared by
dispersing
components (1) and (2) in an aqueous medium which comprises water and,
usually, coalescing
solvents. Alternatively, components (1) and (2) may also be provided as a
single component.
COATING SYSTEM
[0038] The coating compositions disclosed herein may be applied alone or as
part of a
coating system that can be deposited onto a number of different substrates.
The coating system
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typically comprises a number of coating layers. A coating layer is typically
formed when a coating
composition that is deposited onto the substrate is substantially cured,
dehydrated, and/or dried
using methods known in the art (e.g., by thermal heating or via infrared
radiation).
[0039] Suitable substrates that can be coated with the coating composition
disclosed
herein include metal substrates, metal alloy substrates, and/or substrates
that have been metallized,
such as nickel plated plastic. In some embodiments, the metal or metal alloy
can be aluminum
and/or steel. For example, the steel substrate could be cold rolled steel,
electrogalvanized steel,
and hot dipped galvanized steel. Moreover, in some embodiments, the substrate
may comprise a
portion of a vehicle such as a vehicular body (e.g., without limitation, door,
body panel, trunk
deck lid, roof panel, hood, and/or roof) and/or a vehicular frame. As used
herein, "vehicle" or
variations thereof includes, but is not limited to, civilian, commercial, and
military land vehicles
such as cars, motorcycles, and trucks.
[0040] In certain embodiments, the first coating composition is applied onto
at least a
portion of a surface of a substrate that has been cleaned with an alkaline
cleaner that is known in
the art. An example of a suitable alkaline cleaner that may be used in the
present invention
includes CHEMKLEEN (commercially available from PPG Industries, Inc.). In some
embodiments, at least a portion of the alkaline cleaner is rinsed with an
aqueous solution (e.g.,
dionized water) prior to application of the first coating composition.
[0041] After application of the second coating composition disclosed herein, a
primer-
surfacer coating composition is typically applied onto at least a portion of
the second coating
composition or second coating layer. The primer-surfacer coating composition
is typically applied
and cured prior to a subsequent coating composition being applied over the
primer-surfacer
coating composition.
[0042] The primer-surfacer layer that results from the primer-surfacer coating
composition serves to enhance chip resistance of the coating system as well as
aid in the
appearance of subsequently applied layers (e.g., color imparting coating
composition and/or
substantially clear coating composition). As used herein, "primer-surfacer"
refers to a primer
composition for use under a subsequently applied coating composition, and
includes such
materials as thermoplastic and/or crosslinking (e.g., thermosetting) film-
forming resins generally
known in the art of organic coating compositions. Suitable primers and primer-
surfacer coating
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compositions include spray applied primers, as are known to those skilled in
the art. Examples of
suitable primers include several available from PPG Industries, Inc.,
Pittsburgh, Pa., as DPX-
1791, DPX-1804, DSPX-1537, GPXH-5379, OPP-2645, PCV-70118, and 1177-225A.
Another
suitable primer-surfacer coating composition that can be utilized in the
present invention is the
primer-surfacer described in U.S. Patent Application No. 11/773,482.
[0043] It should be noted that in some embodiments, the primer-surfacer
coating
composition is not used in the coating system. Therefore, a color imparting
basecoat coating
composition can be applied directly onto the second coating composition or the
second coating
layer described above.
[0044] In some embodiments, a color imparting coating composition
(hereinafter,
"basecoat") is deposited onto at least a portion of the primer surfacer
coating layer (if present).
Any basecoat coating composition known in the art may be used in the present
invention. It
should be noted that these basecoat coating compositions typically comprise a
colorant.
[0045] In certain embodiments, a substantially clear coating composition
(hereinafter,
"clearcoat") is deposited onto at least a portion of the basecoat coating
layer. As used herein, a
"substantially clear" coating composition is substantially transparent and not
opaque when cured.
In certain embodiments, the substantially clear coating composition can
comprise a colorant but
not in an amount such as to render the clear coating composition opaque (not
substantially
transparent) after it has been cured. Any clearcoat coating composition known
in the art may be
used in the present invention. For example, the clearcoat coating composition
that is described in
U.S. Patent Nos. 5,989,642, 6,245,855, 6,387,519, and 7,005,472 can be used in
the coating
system. In certain embodiments, the substantially clear coating composition
can also comprise a
particle, such as a silica particle, that is dispersed in the clearcoat
coating composition (such as at
the surface of the clearcoat coating composition after curing).
[0046] One or more of the coating compositions described herein can comprise
colorants
and/or other optional materials, which are known in the art of formulated
surface coatings. As
used herein, the term "colorant" means any substance that imparts color and/or
other opacity
and/or other visual effect to the composition. The colorant can be added to
the coating in any
suitable form, such as discrete particles, dispersions, solutions and/or
flakes (e.g., aluminum
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flakes). A single colorant or a mixture of two or more colorants can be used
in the coating
composition described herein.
[0047] Example colorants include pigments, dyes and tints, such as those used
in the paint
industry and/or listed in the Dry Color Manufacturers Association (DCMA), as
well as special
effect compositions. A colorant may include, for example, a finely divided
solid powder that is
insoluble but wettable under the conditions of use. A colorant can be organic
or inorganic and
can be agglomerated or non-agglomerated. Colorants can be incorporated into
the coatings by
use of a grind vehicle, such as an acrylic grind vehicle, the use of which
will be familiar to one
skilled in the art.
[0048] Example pigments and/or pigment compositions include, but are not
limited to,
carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salt
type (lakes),
benzimidazolone, condensation, metal complex, isoindolinone, isoindoline and
polycyclic
phthalocyanine, quinacridone, perylene, perinone, diketopyrrolo pyrrole,
thioindigo,
anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,
anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole
red ("DPPBO red"),
titanium dioxide, carbon black and mixtures thereof. The terms "pigment" and
"colored filler" can
be used interchangeably.
[0049] Example dyes include, but are not limited to, those that are solvent
and/or aqueous
based such as phthalo green or blue, iron oxide, bismuth vanadate,
anthraquinone, perylene,
aluminum and quinacridone.
[0050] Example tints include, but are not limited to, pigments dispersed in
water-based or
water miscible carriers such as AQUA-CHEM 896 commercially available from
Degussa, Inc.,
CHARISMA COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially
available from Accurate Dispersions division of Eastman Chemical, Inc.
[0051] As noted above, the colorant can be in the form of a dispersion
including, but not
limited to, a nanoparticle dispersion. Nanoparticle dispersions can include
one or more highly
dispersed nanoparticle colorants and/or colorant particles that produce a
desired visible color
and/or opacity and/or visual effect. Nanoparticle dispersions can include
colorants such as
pigments or dyes having a particle size of less than 150 nm, such as less than
70 nm, or less than
30 nm. Nanoparticles can be produced by milling stock organic or inorganic
pigments with
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grinding media having a particle size of less than 0.5 mm. Example
nanoparticle dispersions and
methods for making them are identified in U.S. Patent No. 6,875,800.
Nanoparticle dispersions
can also be produced by crystallization, precipitation, gas phase
condensation, and chemical
attrition (i.e., partial dissolution). In order to minimize re-agglomeration
of nanoparticles within
the coating, a dispersion of resin-coated nanoparticles can be used. As used
herein, a "dispersion
of resin-coated nanoparticles" refers to a continuous phase in which discreet
"composite
microparticles", which comprise a nanoparticle and a resin coating on the
nanoparticle, is
dispersed. Example dispersions of resin-coated nanoparticles and methods for
making them are
identified in U.S. Patent Publication 2005/0287348, filed June 24, 2004, U.S.
Provisional
Application No. 60/482,167 filed June 24, 2003, and U.S. Patent Application
Serial No.
11/337,062, filed January 20, 2006.
[0052] Example special effect compositions that may be used include pigments
and/or
compositions that produce one or more appearance effects such as reflectance,
pearlescence,
metallic sheen, phosphorescence, fluorescence, photochromism,
photosensitivity,
thermochromism, goniochromism and/or color-change. Additional special effect
compositions
can provide other perceptible properties, such as opacity or texture. In a non-
limiting
embodiment, special effect compositions can produce a color shift, such that
the color of the
coating changes when the coating is viewed at different angles. Example color
effect
compositions are identified in U.S. Patent No. 6,894,086. Additional color
effect compositions
can include transparent coated mica and/or synthetic mica, coated silica,
coated alumina, a
transparent liquid crystal pigment, a liquid crystal coating, and/or any
composition wherein
interference results from a refractive index differential within the material
and not because of the
refractive index differential between the surface of the material and the air.
[0053] In certain non-limiting embodiments, a photosensitive composition
and/or
photochromic composition, which reversibly alters its color when exposed to
one or more light
sources, can be used in the coating composition described herein. Photochromic
and/or
photosensitive compositions can be activated by exposure to radiation of a
specified wavelength.
When the composition becomes excited, the molecular structure is changed and
the altered
structure exhibits a new color that is different from the original color of
the composition. When
the exposure to radiation is removed, the photochromic and/or photosensitive
composition can
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return to a state of rest, in which the original color of the composition
returns. In one non-
limiting embodiment, the photochromic and/or photosensitive composition can be
colorless in a
non-excited state and exhibit a color in an excited state. Full color-change
can appear within
milliseconds to several minutes, such as from 20 seconds to 60 seconds.
Example photochromic
and/or photosensitive compositions include photochromic dyes.
[0054] In a non-limiting embodiment, the photosensitive composition and/or
photochromic composition can be associated with and/or at least partially
bound to, such as by
covalent bonding, a polymer and/or polymeric materials of a polymerizable
component. In
contrast to some coatings in which the photosensitive composition may migrate
out of the coating
and crystallize into the substrate, the photosensitive composition and/or
photochromic
composition associated with and/or at least partially bound to a polymer
and/or polymerizable
component in accordance with a non-limiting embodiment of the present
invention, have minimal
migration out of the coating. Example photosensitive compositions and/or
photochromic
compositions and methods for making them are identified in U.S. Patent
Application Serial No.
10/892,919, filed July 16, 2004.
[0055] In general, the colorant can be present in any amount sufficient to
impart the
desired visual and/or color effect. The colorant may comprise from 1 to 65
weight percent of the
present compositions, such as from 3 to 40 weight percent or 5 to 35 weight
percent, with weight
percent based on the total weight of the compositions.
[0056] The coating compositions can comprise other optional materials well
known in the
art of formulated surface coatings, such as plasticizers, anti-oxidants,
hindered amine light
stabilizers, UV light absorbers and stabilizers, surfactants, flow control
agents, thixotropic agents
such as bentonite clay, pigments, fillers, organic cosolvents, catalysts,
including phosphonic acids
and other customary auxiliaries.
[0057] In addition to the materials described above, the coating composition
can also
comprise an organic solvent. Suitable organic solvents that can be used in the
coating
composition include any of those listed in the preceding paragraphs as well as
butyl acetate,
xylene, methyl ethyl ketone, or combinations thereof.
[0058] It will be further appreciated that one or more of the coating
compositions that
form the various coating layers described herein can be either "one component"
("1K"), "two
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component" ("2K"), or even multi-component compositions. A 1K composition will
be
understood as referring to a composition wherein all of the coating components
are maintained in
the same container after manufacture, during storage, etc. A 2K composition or
multi-component
composition will be understood as referring to a composition wherein various
components are
maintained separately until just prior to application. A 1K or 2K coating
composition can be
applied to a substrate and cured by any conventional means, such as by
heating, forced air, and
the like.
[0059] The coating compositions that form the various coating layers described
herein can
be deposited or applied onto the substrate using any technique that is known
in the art. For
example, the coating compositions can be applied to the substrate by any of a
variety of methods
including, without limitation, spraying, brushing, dipping, and/or roll
coating, among other
methods. When a plurality of coating compositions are applied onto a
substrate, it should be
noted that one coating composition may be applied onto at least a portion of
an underlying
coating composition either after the underlying coating composition has been
cured or prior to the
underlying coating composition being cured. If the coating composition is
applied onto an
underlying coating composition that has not been cured, both coating
compositions may be cured
simultaneously.
[0060] The coating compositions may be cured using any technique known in the
art such
as, without limitation, thermal energy, infrared, ionizing or actinic
radiation, or by any
combination thereof. In certain embodiments, the curing operation can be
carried out at
temperatures > 10 C. In other embodiments, the curing operation can be carried
out at
temperature < 246 C. In certain embodiments, the curing operation can carried
out at
temperatures ranging between any combination of values, which were recited in
the preceding
sentences, inclusive of the recited values. For example, the curing operation
can be carried out at
temperatures ranging from 120 C - 150 C. It should be noted, however, that
lower or higher
temperatures may be used as necessary to activate the curing mechanisms.
[0061] In certain embodiments, one or more of the coating compositions
described herein
is a low temperature, moisture curable coating compositions. As used herein,
the term "low
temperature, moisture curable" refers to coating compositions that, following
application to a
substrate, are capable of curing in the presence of ambient air, the air
having a relative humidity of
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% to 100 %, such as 25 % to 80 %, and a temperature in the range of -10 C to
120 C, such as
5 C to 80 C, in some cases 10 C to 60 C and, in yet other cases, 15 C to 40 C.
[0062] The dry film thickness of the coating layers described herein can range
from 0.1
micron to 500 microns. In other embodiments, the dry film thickness can be <
125 microns, such
as < 80 microns. For example, the dry film thickness can range from 15 microns
to 60 microns.
[0063] While specific embodiments of the invention have been described in
detail, it will
be appreciated by those skilled in the art that various modifications and
alternatives to those
details could be developed in light of the overall teachings of the
disclosure. Accordingly, the
particular arrangements disclosed are meant to be illustrative only and not
limiting as to the scope
of the invention which is to be given the full breadth of the claims appended
and any and all
equivalents thereof.
EXAMPLES
Example A (comparative example)
[0064] This comparative example describes the preparation of a cationic
electrodeposition
paint containing no added barium. The electrodeposition paint composition was
prepared from a
mixture of the following ingredients:
Resin blend' 1824
Pigment paste 2 223g
Deionized water 1753g
1Cationic resin blend commercially available as E6358 from PPG Ind.
2A pigment paste commercially available as E6364 from PPG Ind.
Example B
[0065] This example describes the preparation of a cationic electrodeposition
paint
containing 25ppm barium metal to control mapping defects. The
electrodeposition paint
composition was prepared from a mixture of the following ingredients:
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Resin blend' 1824
Pigment paste 2 223g
Deionized water 1735.2g
I% barium nitrate 17.8g
Cationic resin blend commercially available as E6358 from PPG Ind.
2A pigment paste commercially available as E6364 from PPG Ind.
Example C
[0066] Unpolished, cold-rolled steel panels (4x12x032) commercially available
from ACT
Laboratories, Inc. were cleaned with Chemkleen CK2010LP/CK181LP (Degreasing
commercially
available from PPG Ind.) and treated with Zircobond (Zircobond pretreatment
commercially
available from PPG Ind.). Phosphated panels (4x12x032) commercially available
from ACT
Laboratories, Inc., C700 No Chemseal Immersion DIW , were used as is. Each one
of the
pretreated panels was connected together, back to back, on the cathode.
Together, they were
electrocoated with the composition of Example A for 2'/ 180volts/ 90 F, and
cured at 350 F for
25 minutes.
Example D
[0067] Unpolished, cold-rolled steel panels (4x12x032) commercially available
from ACT
Laboratories, Inc. were cleaned with Chemkleen CK2010LP/CK181LP (Degreasing
commercially
available from PPG Ind.) and treated with Zircobond (Zircobond pretreatment
commercially
available from PPG Ind.). Phosphated panels (4x12x032) commercially available
from ACT
Laboratories, Inc., C700 No Chemseal Immersion DIW, were used as is. Each one
of the
pretreated panels was connected together, back to back, on the cathode.
Together, they were
electrocoated with the composition of Example B for 2'/ 180volts/ 90 F, and
cured at 350 F for
25 minutes.
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Mapping Results
[0068] When the difference in the film build between two differently treated
substrates
approaches 0, mapping is improved, and the coating is less prone to have
uneven film build on the
zirconium treated substrate. As shown below, the film thickness difference was
smaller in
Example D than in Example C, therein indicating the inclusion of 1% barium
nitrate to the coating
composition improved mapping.
Measured film build (mils)
C700 phosphate steel Zirconium steel Film thickness difference
Example C 0.89 0.58 0.31
Example D 0.79 0.69 0.19
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